Several techniques exist for ice detection and thickness measurement. The related hardware is either mechanical, acoustical or optical in nature. U.S. Pat. No. 5,400,144 of the present inventor (Method and Apparatus for Remote Detection and Thickness Measurement of Ice or Liquid Layer) describes an optical method incorporating a laser and a sensor (video camera or diode array) to produce a certain pattern on the surface due to internal reflection of the laser light within the solid or liquid layer measured. The image obtained by the sensor, and in particular the diameter of illuminated zones, can be interpreted in terms of the thickness of the layer. The technique is best suited to light colored surfaces and layer thicknesses from 500 .mu.m to several centimeters. It is not as effective on dark surfaces or polished (or semi-polished) metallic surfaces.